However, if you don't live in an area with a climate similiar to Japan, it can be very uncomfortable to stick with these rules. For example, I live in the Southern United States, and our climate isn't exactly comparable. This year, it's already been up to 85F in April. Just based on temperature, that's ro/sha weather.
So what do you do then? No one wants to look like they don't know what they're doing, but you don't want to die from heat stroke either. My take? Do what is comfortable. Explain if you have to. But don't kill yourself! While I haven't gotten to ro/sha just yet, I have been wearing some hitoe, depending on the weather of the day. For example, it was 60F when I went to tea ceremony the other day, and I wore awase. But a few weeks ago it was 80F, and I wore hitoe, even though it was early April. I'm not bold enough to switch to ro/sha until it becomes muggy (like it does every summer here). But you can bet that by the end of May, I'll probably be in ro/sha. And I'll probably be wearing it through September, since it doesn't turn cooler until October around here.